Drive for a reduced scale track-laying utility vehicle

ABSTRACT

A unique drive arrangement for a hydraulically powered tractor unit characterized by its uniform and efficient power distribution is disclosed. In a first embodiment, one pool of each of two dual spool control valves regulates the flow of hydraulic fluid between individual pumps and motors for each track of the vehicle, the second spool of each of the control valves being available to actuate accessories on the vehicle. In a second embodiment, a single pump through a dual spool valve operates the accessories while a tandem pump through individual single spool valves operates each of the drive motors.

[ Feb. 29, 1972 United States Patent Nichter 2,381,109 8/1945Cartlidge..............................18016.48 2,980,193 4/1961Baudhuinetal......................180/6.48

[54] DRIVE FOR A REDUCED SCALE TRACK-LAYING UTILITY VEHICLE [72]lnventor: David E. Nichter, R.R. 2, Churubusco,

Jan. 5, 1970 Primary ExaminerBenjamin Hersh Assistant Examiner.lohn A.Pekar Attorney.leffers and Richert [22] Filed:

tor unit characterized by its uniform and efficient power dis tributionis disclosed. In a first embodiment, one pool of each [52] U.S.Cl. [51]Int. [58] Field of of two dual spool control valves regulates the flowof hydraulic fluid between individual pumps and motors for each track ofR f n Cited the vehicle, the second spool of each of the control valvese ere ces being available to actuate accessories on the vehicle. 1n aUNITED STATES PATENTS second embodiment, a single pump through a dualspool valve operates the accessories while a tandem pump through in-8/1961 dividual single spool valves operates each of the drive motors.

3 Drawing Figures 5 Claims,

PAIENTEBFEB29 I972 SHEET 2 OF 3 DAVID E. NICHTER BY gw wwd, %.7

ATTORNEYS PAIENTEBFEB 29 I972 SHEET 3 OF 3 INVENTOR DAVID E. NICHTER BY%7 ATTORNEYS BACKGROUND OF THE INVENTION This invention relates to aunique drive arrangement for a hydraulically powered tractor unit andmore especially to such a drive arrangement in a reduced scaletrack-laying utility vehicle. Hydraulic drive arrangements are of coursenot new and have been used for a number of years in large-scaleearthmoving equipment such as common bulldozers, however, the hydraulicdrive arrangements used in these large-scale machines are complex andexpensive and not readily adapted to a smaller scale machine.

Small-scale utility vehicles are, of course, also known and arecharacterized for example by the well-known home garden tractor. Thesesmall-scale machines are typically powered by a gasoline engine and thedrive arrangement consists of one or more V-belts and appropriatepulleys to transmit the energy from the engine to the wheels. SuchV-belt drives are of course limited in the power which they can transmitand generally involve some slippage of the belt particularly in theclutching or gear-changing portion of the drive. Under suchcircumstances, the life of the belt is generally short.

The recent financial success of the snow mobile has generated severalother recreational small-scale vehicles termed all-terrain vehicles(ATV). Such ATVs are designed for recreational use and are againgenerally belt driven and suffer from the aforementioned defects. TheATVs and garden tractors that have gone to any type of hydraulic systemhave done so to effect clutching and speed change but have not providedan integrated utility vehicle.

SUMMARY OF THE INVENTION The vehicle of the present invention does notfall into any of the three above-mentioned categories. The invention isdirected to a small-scale track-laying hydraulically powered tractorunit capable of pulling substantially greater loads and of operatingsubstantially more complex and powerful auxiliary equipment than thestandard garden tractor, it has only limited recreational use and thisis a distinctly secondary characteristic and it is substantially smallerand more maneuverable than the bulldozer class of equipment. The vehicleof the present invention has a sprocket which drives the chainassociated with each track and a spring-loaded idler sprocket associatedwith each track which prevents damage to the system should the sprocketand chain fail to properly mesh. The driving sprockets for each trackare in turn driven by hydraulically powered motors individual to thatparticular sprocket. The individual motors are in turn controlled byindividual control valves which receive their hydraulic energizationeither from separate pumps or from the two outlets on a dual outlet ortandem hydraulic pump. Hydraulic power for accessories such as atiltable blade, back hoe, or fork lift is uniformly derived from each ofthe two pumps in the first instance and from a second pump in theembodiment relying on a tandem pump for the primary or motive power.Such accessories generally comprise push and lift pistons however, theirprecise nature is not particularly important to the present invention.

Accordingly, it is one object of the present invention to provide auniform and efficient economical power distribution system for asmall-scale hydraulically powered utility vehicle.

It is another object of the present invention to provide a hydraulicallydriven utility vehicle having auxiliary or accessory power readilyavailable.

It is a further object of the present invention to provide a drivearrangement which eliminates the belt drive arrangements whichcharacterize the prior art.

It is a still further object of the present invention to provide aversatile small-scale bulldozer which has particular utility inrestricted spaces or for small jobs which do not warrant the use of astandard bulldozer.

It is a salient object of the present invention to provide a utilityvehicle which has uniform drive provided to each track and whichoptimizes the power distribution both for the motive power of thevehicle and for the auxiliary or accessory devices.

These and other objects and advantages of the present invention willappear more clearly from the following detailed disclosure read inconjunction with the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view of thetractor unit of the present invention;

FIG. 2 is a partially schematic diagram of the power drive arrangementin one embodiment of the present invention; and

FIG. 3 is a partially schematic view of another embodiment of the powerdrive arrangement of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning first to FIG. 1, thetractor unit or crawler is seen to consist of a body indicated generallyby the numeral 11 having a seat 13 to accommodate an operator and havingaccessible control levers 15, 17, 19 and 21. The body 11 is supported ona pair of drivable tracks 23 and 25 which are drivenby a drive chain 27and a driving sprocket wheel 29. Each of these tracks also has an idlersprocket wheel 31 which is spring-loaded by the springs 33. Thespring-loading serves both to maintain the proper tension on the trackand to prevent damage in the event that a stone or other bit of foreignmatter becomes engaged between the chain 27 and one of the sprocketwheels 29 or 31. The tension in the spring 33 is made adjustable by useof a threaded yoke so that the proper tension may be maintained at alltimes. Track support is derived from a track carrier 35 which consistsof a number of bogie wheels 37 held in position by means of a slidebeam. The track 23 is made up of a chain 27 having a series of trackshoes 39 bolted to the chain so that they may be removed to effectrepair of the chain or the shoe as needed. The shoes 39 may be eitherflat or have one or two gripping cleats 41 as desired. FIG. 1 alsoillustrates the hydraulic fluid reservoir 43 symmetrically disposedabout and underneath the operators seat. Clearly, two hydraulic fluidreservoirs could be symmetrically disposed on either side of the seatand connected in either series or parallel.

Turning now to FIG. 2, power for the crawler is derived from a gasolineengine 47 which may be of either the two or four cycle variety and whichin one preferred embodiment was a nine to l2 horsepower engine. Twochain drives 49 and 51 are taken from the shaft of the engine 47 todrive two identical pumps 53 and 55 although a Vbelt drive at this pointcould be utilized. The pumps 53 and 55 derive their hydraulic fluidsupply in parallel from the reservoir 43 by way of the conduits 57'and58. Due to the symmetry, the fluid path for the drive to the left orlower track will be discussed in detail in being understood that thedrive for the right track functions in precisely the same manner. Theoutlet of the single-inlet single-outlet pump 55 is fed by way ofconduit 59 to the inlet of a dual spool control valve 61. The conduits63 and 65 are associated with the lever 21 in FIG. 1 while the conduits67 and 69 are associated with lever 19 of FIG. 1. With levers 19 and 21in their neutral position, the fluid flow is directly through thecontrol valve 61 to the outlet conduit 71 which passes the hydraulicfluid through a filter 75 and back into the reservoir 43. Two reservoirscould be provided and connected in series by a conduit to provide asymmetry in the distribution of the weight and space on the vehicle,however I prefer a single large reservoir 43 which is symmetrical inconfiguration and can be contoured to form a portion of the operatorsseat. A large reservoir having two inlets for the return of thehydraulic fluid as well as two outlets to supply the fluid to the twoseparate pumps is preferable and has a number of advantages over twosmall supply tanks connected in series and having a single inlet and asingle outlet with a subsequent T to supply fluid tothe individualpumps. A large oil supply provides additional weight on the rear end ofthe crawler and allows it to be provided with a large capacity scoop orbucket and still prevent tipping when the bucket is loaded. A large oilsupply is also desirable because this hydraulic fluid may become quitehot under conditions of heavy usage. Parallel flow to and from thereservoir is desirable over a single inlet and outlet used inconjunction with Ts because a more uniform and equal distribution ofhydraulic fluid flow is attainable. This large tank may also be providedwith baffles similar to those found in an ordinary automobile gasolinetank which will tend to maintain the oil distribution and therefore theweight in the tank at a uniform distribution.

Hydraulic motors of the type contemplated in the present invention may,for example, be purchased from Warner-Motive, a Division of Borg-WarnerCorporation, having general offices in Auburn, Indiana. Hydraulicdirectional control valves may be purchased from Cross Manufacturing,Inc., Lewis, Kansas. Valves, motors and the other elements illustratedin block diagram form in FIGS. 2 and 3 may be purchased fromStover-Winsted Company, Inc., Indianapolis, Indiana.

Returning now to the dual spool control valve 61, if the control lever19 is pushed forward, the hydraulic fluid enters the valve by conduit59, passes into the conduit 69, through the motor 79, back to thecontrol valve by way of conduit 67 and hence out of the outlet conduit71. With the lever in this position, the motor 79 serves to drive theleft track in a forward direction. If the lever 19 is now pulled backfrom its neutral position, oil enters the control valve by conduit 59,travels to the motor by way of conduit 67, passing through the drivemotor 79 and returning to the control valve by way of conduit 69 andhence out of the control valve through conduit 71. With this reverseddirection of fluid flow, the left track is driven in a reversedirection. Similar control is effected by operating the lever 17 tocause the hydraulic fluid to pass into the motor 81 selectively by wayof either conduit 83 or 85 to similarly control the forward reversedrive of the right track. Thus, forward motion of the crawler iseffected by pushing levers I7 and 19 forward while reverse motion of thecrawler is effected by pulling these same two levers back. To turn thecrawler to the right, one may elect to leave lever 17 in its neutralposition and merely push lever 19 forward thus energizing only the lefttrack or for a sharper turn, the left track may be energized in aforward direction and the right track energized in a reverse directionby pulling the lever 17 backward. Similar operations my be utilized toeffect sharp or gradual left turns.

Returning again to the dual-spool control valve 61 with lever 21 in itsneutral position, there is no fluid flow in either of the conduits 63 or65, however, pushing this control lever in one direction causes a fluidflow, for example, through the pipe 63 to push or lift piston 87 andback through the conduit 65 while the reverse position of the levercauses the fluid flow to reverse and the operation of the piston 87 tochange directions. If we now assume that both levers 19 and 21 are intheir forward position, the fluid flow through the valve 61 will enterby way conduit 59 pass out of the valve by way of conduit 63, andreenter by way of conduit 65, again pass out of the valve by way ofconduit 69 and return by way of conduit 67, and finally pass out of thecontrol valve by way of conduit 71. Simple energy considerations willlead one to the conclusion that when the piston 87 is being operated,less energy is available from the control valve 69 to power the drivemotor 79 and hence, it should be' clear that it is undesirable toattempt to use a dual-spool control valve to control both of the drivemotors 79 and 81. This is the reason for providing separate pumps andseparate control valves for the two drive motors and for tapping offeach of the control valves for the accessory or auxiliary power whichtypically will not be used to any extent while the crawler is moving.Thus, while the outlets 89 and 91 of the right control valve are notillustrated as actuating anything, it is anticipated that they will besimilarly connected to other push or lift pistons similar to the piston87. Under these circumstances a uniform and efficient utilization of thepower available from the pumps 53 and 55 is achieved.

This straightline tracking and uniform utilization of the availablepower may also be achieved by the hydraulic system illustrated in FIG.3. In FIG. 3, those portions of the hydraulic system which have the samefunction are denominated by the same reference numerals and only thevariations from FIG. 2 will be discussed. Fluid is again supplied to thepumps by way of conduits 57 and 58 from the reservoir 43 and pump 53 isagain a single-inlet single-outlet pump supplying hydraulic fluid to adual-spool control valve 93. This dual-spool control valve has provisionfor actuating two auxiliary or accessory devices by way of the pair ofterminals and 97 and the pair 99 and 101. The outlet from the dualspoolcontrol valve allows the fluid to flow back through the filter 76 andinto one portion of the reservoir 43 as described before. The secondhydraulic pump in this instance is a single-inlet dual-outlet pump 103which provides equal energy through conduits 105 and 107 to each of twosingle-spool control valves 109 and 111. Each of these individual valvesis in turn connected to energize one of the motors 81 and 79 to supplythe motive power for the tractor. The outputs from each of the valves109 and 111 is joined to the return conduit 113 to the filter 75. Thetandem or dual-outlet pump 103 serves to provide the equal energies tothe two motors 79 and 81 as discussed earlier and this embodiment wouldbe advantageous over that discussed in respect to FIG. 2 on a piece ofearth-moving equipment which required that the tracks be energized atthe same time that an auxiliary or accessory item was being energized.This again, is because of the nature of the dual-spool control valvesand their unequal distribution of energy when both spools are supplyingenergy at the same time.

The present invention provides a small-scale utility vehicle which canbe operated in barns, trailer courts, between houses constructed closetogether, in the removal of snow from city sidewalks and service stationdriveways, as an aid in pipeline construction as well as of electricaland underground communication cables, in a basement or on top of largebuildings during a construction process. Numerous modifications on thetwo embodiments disclosed will readily suggest themselves to those ofordinary skill in this art, which modifications would be within thescope and spirit of the present invention.

I claim:

1. A reduced scale track-laying hydraulically powered tractor unitcomprising:

3 a body having an operator's seat adapted to accommodate an operatorand having a plurality of control levers adapted to provide accessibleoperator control, at least one tractor accessory movably mounted on saidbody near one end of said tractor unit, a pair of drivable tracksadapted to support said body, and driving means supported by said bodyand operatively engaging said tracks to provide locomotion for saidtractor unit, said driving means comprising;

a gasoline engine, a first single-inlet single-outlet pump adapted to bedriven by said engine and to provide hydraulic accessory power to anaccessory, a second single-inlet dual-outlet pump adapted to be drivenby said engine, a pair of hydraulic motors permanently connected todrive respective ones of said pair of drivable tracks, first controlmeans for selectively gating a fluid from one of said dual outlets to afirst of said motors, second control means for selectively gating afluid from the other of said dual outlets to the other of said motors,said first and second control means being actuated by first and secondof said. control levers, and fluid reservoir means for providing a fluidto both said pumps, said fluid reservoir means being symmetricallydisposed about said operator seat so as to present approximately equalloads to each said track and to provide counterbalancing at the tractorunit end remote from said accessory end.

2. The tractor unit of claim 1 wherein said fluid reservoir meanspartially surrounds said operator seat, further comprising springlloadedidler sprocket wheels engaging said drivable tracks and adapted tomaintain the proper tension on said drivable tracks and to yield whenthe tension on said drivable tracks exceeds a predetermined value.

3. A hydraulically driven track-laying utility vehicle comprising:

a body having an operators seat adapted to accommodate an operator andhaving a plurality of control levers adapted to provide accessiblecontrols, a pair of drivable tracks adapted to support said body, anddriving means supported by said body and operatively engaging saidtracks to provide locomotion for said vehicle, said driving meanscomprising; gasoline engine, a first single-inlet single-outlet pumpadapted to be driven by said engine, a second single-inlet singleoutletpump adapted to be driven by said engine, a pair of hydraulic motorspermanently connected to drive respective ones of said pair of drivabletracks, first control means for selectively gating a fluid from theoutlet of said first pump to a first of said motors, second controlmeans for selectively gating a fluid from the outlet of said second pumpto a second of said motors, said first and second control means beingresponsive to actuation of first and second of said control levers, areservoir for containing hydraulic fluid having inlet means and outletmeans, said outlet means connected to the inlets of each said first andsecond pumps, said reservoir being symmetrically disposed about saidoperator seat near one end of said vehicle so as to presentapproximately equal loads to each said track and to providecounterbalancing weight at said one end of said tractor, and filtermeans completing said hydraulic circuit by connecting the first andsecond control means to said reservoir inlet means.

4. The vehicle of claim 3 wherein said reservoir partially surroundssaid operator seat further comprising spring-loaded idler sprocketwheels engaging said drivable tracks and adapted to maintain the propertension on said drivable tracks and to yield when the tension on saiddrivable tracks exceeds a predetermined value.

5, The vehicle of claim 4 further comprising baffle means within saidreservoir for maintaining a relatively uniform distribution of fluidtherein.

1. A reduced scale track-laying hydraulically powered tractor unitcomprising: 3 a body having an operator''s seat adapted to accommodatean operator and having a plurality of control levers adapted to provideaccessible operator control, at least one tractor accessory movablymounted on said body near one end of said tractor unit, a pair ofdrivable tracks adapted to support said body, and driving meanssupported by said body and operatively engaging said tracks to providelocomotion for said tractor unit, said driving means comprising; agasoline engine, a first single-inlet single-outlet pump adapted to bedriven by said engine and to provide hydraulic accessory power to anaccessory, a second single-inlet dualoutlet pump adapted to be driven bysaid engine, a pair of hydraulic motors permanently connected to driverespective ones of said pair of drivable tracks, first control means forselectively gating a fluid from one of said dual outlets to a first ofsaid motors, second control means for selectively gating a fluid fromthe other of said dual outlets to the other of said motors, said firstand second control means being actuated by first and second of saidcontrol levers, and fluid reservoir means for providing a fluid to bothsaid pumps, said fluid reservoir means being symmetrically disposedabout said operator seat so as to present approximately equal loads toeach said track and to provide counterbalancing at the tractor unit endremote from said accessory end.
 2. The tractor unit of claim 1 whereinsaid fluid reservoir means partially surrounds said operator seat,further comprising spring-loaded idler sprocket wheels engaging saiddrivable tracks and adapted to maintain the proper tension on saiddrivable tracks and to yield when the tension on said drivable tracksexceeds a predetermined value.
 3. A hydraulically driven track-layingutility vehicle comprising: a body having an operator''s seat adapted toaccommodate an operator and having a plurality of control levers adaptedto provide accessible controls, a pair of drivable tracks adapted tosupport said body, and driving means supported by said body andoperatively engaging said tracks to provide locomotion for said vehicle,said driving means comprising; a gasoline engine, a first single-inletsingle-outlet pump adapted to be driven by said engine, a secondsingle-inlet single-outlet pump adapted to be driven by said engine, apair of hydraulic motors permanently connected to drive respective onesof said pair of drivable tracks, first control means for selectivelygating a fluid from the outlet of said first pump to a first of saidmotors, second control means for selectively gating a fluid from theoutlet of said second pump to a second of said motors, said first andsecond control means being responsive to actuation of first and secondof said control levers, a reservoir for containing hydraulic fluidhaving inlet means and outlet means, said outlet means connected to theinlets of each said first and second pumps, said reservoir beingsymmetrically disposed about said operator seat near one end of saidvehicle so as to present approximately equal loads to each said trackand to provide counterbalancing weight at said one end of said tractor,and filter means completing said hydraulic circuit by connecting thefirst and second control means to said reservoir inlet means.
 4. Thevehicle of claim 3 wherein said reservoir partially surrounds saidoperator seat further comprising spring-loaded idler sprocket wheelsengaging said drivable tracks and adapted to maintain the proper tensionon said drivable tracks and to yield when the tension on said drivabletracks exceeds a predetermined value.
 5. The vehicle of claim 4 furthercomprising baffle meaNs within said reservoir for maintaining arelatively uniform distribution of fluid therein.